The invention pertains to natural gas line lead-in assemblies utilizing inner conduit structure encased within a convoluted metal sheath.
Natural gas supply conduits for residential and industrial use are buried several feet below the ground surface, and it is now common practice to utilize synthetic plastic, such as polyethylene, in the manufacture of high pressure gas supply tubing. However, as gas meters and other components and fittings employed in natural gas systems are normally located above ground level safety codes require that above ground level gas conduit be metal, or protected by metal, in order to minimize the possibility of the conduit being inadvertently severed or the gas ignited.
Accordingly, gas lead-in assemblies are commonly employed in natural gas supply systems at the location where the buried polyethylene tubing approaches the gas meter or other apparatus mounted above the ground level. Such assemblies usually consist of a metal or nonmetal lower conduit adapted to be coupled to the polyethylene supply tubing, and in communication with a fitting adapted to be attached to the above ground level fitting, meter, etc. The assembly includes an outer metal tube or sheath in order to comply with the safety code with respect to metal protection being required above ground level, and lead-in assemblies of this type include a number of structural variations, one of which being shown in U.S. Pat. No. 3,861,719.
Heretofore, natural gas lead-in assemblies have not met all the prerequisites desired, such as low cost, ease of handling and installation, adaptability to most types of installations, and ability to be readily formed or shaped by hand without kinking of the tubing.